Two recent studies raised the possibility that calcium supplements may increase the risk of cardiovascular disease. Consequently, a number of readers have wondered if they should take calcium, and if so, how much. As most people reading know, this is an important question relating to vitamin D, as vitamin D increases your ability to absorb calcium.
Professor Robert Heaney of Creighton University, together with Dr. John Hathcock and others at the Council for Responsible Nutrition, recently reviewed all the studies on calcium supplements and cardiovascular disease.
The authors made several points, including the following:
- Calcium is the fifth most abundant element in the human body, with >99% residing in the skeleton.
- Thousands of milligrams of calcium passively diffuse into and out of bone on a daily basis.
- The kidneys filter as much as 10,000 mg of calcium each day, with ~98% retained by the kidneys.
- Fifty-four percent of Americans did not meet the estimated average requirement for calcium with diet alone.
- Emerging evidence suggests that calcium supplementation may be associated reduced risk of the development of colon polyps, cancers, and pre-eclampsia.
- Over the last two decades, calcium supplementation has been increasing, with 43% of the US population and 70% of older women now using calcium supplements. During this same time, cardiovascular disease has been steadily decreasing.
- Studies show calcium slightly increases cardiovascular disease, a few show it slightly decreases cardiovascular disease, but most show no effect on cardiovascular disease.
- Among 16 studies reviewed in this article involving >358,000 individuals, there was no indication of a connection between calcium intake and atherosclerotic heart disease or stroke.
That said, some people take too much calcium. They don’t seem to realize that calcium intake recommendations are for total calcium intake, not supplement intake. It is very difficult to get no calcium in your diet. Also, realize that higher vitamin D levels will increase calcium absorption, up to 32 ng/ml at which point higher levels will not increase absorption any further.
If you continue to supplement with calcium, be sure to estimate your dietary intake, subtract it from the amount recommended for your age, and supplement with the remainder. It is probably better to get calcium through your diet than through supplements, which usually means some form of dairy consumption, but don’t forget calcium is also in things like fish (with bones) and green vegetables.